Paraplegia (paralysis of the lower part of the body) resulting from spinal cord ischemia during an operation, such as thoracoabdominal aorta operation, thoracic descending aortic aneurysm operation and spinal cord injury operation, is a complication that significantly damages the quality of life (QOL) of a patient.
Various methods for protecting the spinal cord have been developed until now; however, such methods have not achieved complete prevention of paraplegia.
A method utilizing evoked spinal cord potentials can be recognized as a method for monitoring paraplegia during an operation. The said method is for recording, as electromagnetic waveforms, current running through the spinal cord caused by electric stimulation, and observing changes, such as an amplitude drop of the waveforms, when the spinal cord is experiencing ischemia and the conduction of the electricity becomes poor.
Conventionally, a stimulating electrode is placed at the scalp or the periphery of the cervical spinal cord dura mater to obtain waveforms from a recording electrode placed at a periphery of the thoracolumber dura mater or a muscle of the leg.
However, such a conventional evoked spinal cord potential monitoring method has various problems as follows: (1) when inserting an electrode into the periphery of the dura mater, it is necessary to insert and place the electrode at the periphery of the dura mater on the prior day of the operation in order to avoid a complication of bleeding because heparin is used during the operation; (2) the electrode cannot be used for an emergency operation; and (3) in a case where the potential is recorded from a muscle of the leg, the potential cannot be recorded if a muscle relaxant is used during the surgery.
Due to the drawbacks described above, narcoses and potential monitoring methods face significant difficulties.